With modern vehicle design provides an operator satisfactory forward visibility during vehicle operation, vision in side and rear directions is often obstructed. To some extend operator vision is augmented by proper placement of mirrors on the vehicle. However, mirrors do not completely eliminate blind spots. For example, it is difficult to provide a satisfactory view toward the rear of a vehicle using mirrors due to obstructions caused by the body of the vehicle. Operator vision toward the rear of the vehicle is further impeded by the relatively large distance from the operator position to the rear of the vehicle common to tractor-trailer combinations and other large vehicles.
Mirrors further limit visual clues necessary for operator judgment of distance to an obstruction by limiting operator depth perception. This is a particular problem when backing a vehicle when the operator requires accurate distance information to maneuver a vehicle (e.g., a semi-tractor trailer) toward an obstruction such as a loading dock. Because of the relatively large distance between the operator and the rear of the vehicle, smaller obstructions may go unnoticed. This is also true in blind areas one either side of a vehicle where direct driver observation is not possible and mirror systems provide incomplete coverage.
Various systems have been proposed in addition to mirrors to augment operator vision. These systems include visual systems using television cameras and monitors to allow visual observation of areas not viewable through mirrors. Television augmentation is relatively expensive, requires the operator to divert his or her attention from other visual systems, and provides limited clues to determine distance to an obstruction.
Electronic obstruction detecting and ranging systems use ultrasonic, radar and infrared emitters and receivers to bounce energy off an obstruction. The systems measure the time required for the emitted energy to travel to and from the obstruction to determine a distance to the obstruction.
Starke et al. U.S. Pat. No. 4,903,004, incorporated herein by reference, describes a distance measuring and signalling system for a vehicle for measuring distances to obstructions such as behind a vehicle being backed up. An array of transducers are mounted on a support such as a rear bumper of the vehicle. A pulsed signal is timed as it is converted to an ultrasonic wave signal and its echo detected. The calculated distance is displayed on a three digit display mounted on a dashboard of the vehicle. The system includes ultrasonic transmitting/receiving units, a control unit and a digital display unit.
Tendler U.S. Pat. No. 4,937,796 describes a method and apparatus for providing a voice alert to a vehicle operator. The apparatus uses sonar to detect a distance from the rear of a vehicle to a structure such as a loading dock to which the vehicle is being backed. A device converts a detected range into an audible call out of the distance from the back of the vehicle to the structure.
Naruse U.S. Pat. No. 4,674,073 describes an apparatus for use in a vehicle for ultrasonically locating and ranging an object in relation to the vehicle. A plurality of ultrasonic transmitting and receiving elements are alternately arranged in a linear array and sequentially activated to detect and locate an object. A digital display shows the location and distance to a detected object.
Chev U.S. Pat. No. 4,626,850 describes an apparatus for use in a vehicle for ultrasonically locating and ranging an object in the vicinity of the vehicle. An ultrasonic transducer is rotated in azimuth to scan an area for objects. Audio and visual display of distance and direction to a detected object are provided.
Lee U.S. Pat. No. 4,943,796 describes a display unit attachable to an inside rear view mirror of an automobile for displaying distance to an object behind the vehicle using ultrasonic sensors.
While the prior art describes ultrasonic detection and ranging devices, conventional visual distance displays require the vehicle operator to divert attention away from other systems to observe the device display. Although Lee describes a display mounted on an inside mirror so that a distance display is observable near the mirror, the system still requires the vehicle operator to divert his or her vision from the mirror to the attached display. Further, this latter system is not usable with tractor-trailer combinations not having an inside rear view mirror.
Accordingly, an object of the invention is to provide an vehicular digital distance display system for providing precise obstruction distance information to an operator without requiring the operator to divert attention away from other visual systems.
Another object of the invention is to provide an digital distance display system usable with tractor-trailer combinations and other vehicles having an obstructed rear view.
Another object of the invention is to provide a digital distance display system which minimizes operator distraction until an obstruction is detected within a predetermined hazard or threshold range.
Another object of the invention is to provide a non-obtrusive vehicular mount for a distance measuring sensor.